1. Field of The Invention
The present invention relates generally to devices for removing atheromatous or blood clot material from blood vessels, and more particularly, to an atherectomy device adapted to be inserted percutaneously and including an expandable, rotatable cutting head as well as a method for using such a device to remove an atheroma or a blood clot.
2 Description of the Prior Art
Atheromatous material consist of fat particles and calcium deposited upon the inner walls of arteries. As these deposits increase in size, they restrict the artery lumen, reducing the flow of blood therethrough. The resulting reduction in blood flow may cause an inadequate supply of blood to reach an organ or other part of the body supplied by such artery beyond the point of restriction. If the narrowing of the artery becomes very severe, the artery may totally occlude, resulting in death of the tissue supplied by the artery, or significantly compromising tissue function.
Several methods are currently available to form a channel through a blocked artery. Initially, a guidewire was used to gently probe a channel through the blockage in the artery to reach the normal artery beyond. Once the guidewire was advanced through the blockage, an angioplasty balloon catheter was passed over the guidewire and inflated to dilate the blockage. However, this method is known to cause tears in the artery in order to accommodate the inflated balloon. Moreover, such method does not remove the atheromatous material.
More recently, efforts are being made to use laser energy to vaporize atheromatous material within a blood vessel. However, this method of using laser energy has limited application at the present time.
Several techniques have been proposed for opening a blocked artery using a catheter device to physically remove atheromatous material from the inner walls of blood vessels. For example, U.S. Pat. No. 4,669,469 (Gifford, III. et al.) describes an atherectomy catheter device having a cylindrical housing of a fixed diameter at the distal end thereof. The cylindrical housing includes a cutout on one side thereof, and a rotating cutter is slidably mounted within the cylindrical housing for cutting any deposits forced into the cutout. The cutter is rotated by a motor drive unit coupled to the cutter by a flexible drive cable. The device is advanced into a blood vessel over a guidewire. An inflatable balloon in positioned outside the cutter housing opposite the cutout to urge the housing toward the atheroma to force the atheroma into the cutout. Atheromatous material shaved from the wall of the artery is stored at the end of the cutter housing.
U.S. Pat. No. 4,273,128 (Lary) describes a surgical instrument including a pair of static cutting blades placed at the distal end of a balloon catheter to create longitudinal incisions in a narrowed or occluded artery. The static blades do not rotate, but merely create longitudinal incisions to facilitate dilation of the vessel using the inflatable balloon. The static cutting blades do not cut or shave away the atheromatous material or reduce it to a size which will permit aspiration.
U.S. Pat. No. 4,465,072 (Taheri) describes a needle catheter for scraping or thrombosing vascular walls, particularly in the treatment of varicose veins. The needle catheter includes an inflatable balloon mounted at the distal tip thereof. The balloon carries a plurality of abrasive burrs or ribs on the outer surface thereof. The catheters advance into the vessel, with the balloon initially being deflated. The balloon is then inflated, and the catheter is moved longitudinally up and down in the vessel to scrape the walls of the vessel. The function of the needle catheter is to promote thrombosis of the walls of the vein; however, scraping of the inner lining of the blood vessel causes damage thereto, making the blood vessel more prone to clotting. The described needle catheter is not intended for removing atheromatous material or blood clots from the inner walls of a blood vessel.
A catheter described by Bard includes an inner corkscrew-type guidewire which is inserted through a blocked vessel. A rotating catheter with a circumferential blade is advanced over the wire, and a core of the occluding material is removed to form a channel. Once this channel has been created, it is enlarged using a conventional dilation balloon catheter. Thus, the Bard catheter does not completely remove atheromatous material from the blood vessel. It creates a channel into which a balloon may be placed and the artery dilated. Moreover, the catheter which includes the circumferential blade is of a fixed diameter.
In "new InterVentional Technology", The American Journal of Cardiology, Oct. 1, 988, Volume 62, pages 12F-24F, a transluminal extraction catheter (TEC) for cutting away atherosclerotic plaque from vessel walls is described. Developed jointly by InterVentional Technologies, Inc. and Duke University's Interventional Cardiac Catheterization Program, the transluminal extraction catheter includes a motorized, rotating stainless steel element equipped with a conical cutting head. The cutting head is mounted on a flexible torque tube incorporating a vacuum system that allows retrieval of excised material. The device is controlled by a steerable guidewire. However, the diameter of the cutting head is fixed, and the size of the cutting head is limited by the size of the opening made in the blood vessel where the device is introduced.
In "Recanalization of Obstructed Arteries with a Flexible, Rotating Tip Catheter", Radiology, November, 1987, Volume 165, No. 2, pages 387-389, Kensey, et al. describe a catheter including a rotating cam at the distal tip rotated by an internal torsion drive wire. The rotating cam is advanced through the blockage to form a hole therethrough. Once again, however, the rotating cam is of a fixed diameter, and the size of such rotating cam is limited by the opening made in the blood vessel where the device is introduced.
In "Removal of Focal Atheromatous Lesions By Angioscopically Guided High-Speed Rotary Atherectomy", Journal of Vascular Surgery, February, 1988, Volume 7, No. 2, pages 292-300, Ahn, et al. describe a high-speed rotary atherectomy device inserted over a guidewire and directed with an angioscope. The atherectomy device includes a diamond-coated brass burr welded to a flexible drive shaft which rotates and tracks along a central coaxial guidewire. The drive shaft is connected to a turbine driven by compressed air. The drive shaft is encased with a protective plastic sheath. The diamond-coated brass burrs are available in various sizes selected to match the luminal diameter of the artery. The high-speed rotary burr grinds occluding atheroma into fine particles. However, the diameter of any particular selected burr is fixed and is limited by the size of the opening made in the blood vessel where the device is introduced.
While not intended to remove atheromatous material, balloon dilation catheters have long been used to dilate restricted arteries. Mechanical expandable devices are also known for re-establishing desired blood flow through a blood vessel. For example, U.S. Pat. No. 4,585,000 (Hershenson) describes an intravascular expandable device adapted to be inserted within and through the lumen of a blood vessel. The device includes a distal tip portion which may be mechanically expanded after reaching a stenotic area to dilate the vessel. Similarly, U.S. Pat. No. 3,557,794 (VanPatten) discloses a blood vessel dilation catheter using a slotted tube to form several expandible beams; a central retractor wire can be tensioned by a rotating calibrated drum to cause the beams to bow outwardly by a varying degree. However, neither of the devices disclosed by Hershenson and VanPatten are adapted to remove atheromatous material from a blood vessel, nor are they adapted to be rotated by a motor drive. Expandible devices are also known in the art for scraping the walls of a uterus, as opposed to a blood vessel. For example, U.S. Pat. Nos. 1,155,169 (Starkweather) and 3,670,732 (Robinson) both describes surgical instruments used to remove accumulated material from the walls of a uterus. The Starkweather device includes a series of expandable wires which are initially elongated during insertion, and which are thereafter compressed to form an expanded shape; the instrument is manually rotated to scrape and clean the walls of the uterus. The Robinson device uses a pair of fingers which are initially compressed within a tube during insertion The fingers are then expelled, and the device is manually rotated to wipe the fingers against the uterine wall. A vacuum source withdraws loosened material from the uterus. Clearly, the devices disclosed by Starkweather and Robinson could not be used to remove atheromatous material or blood clots from a blood vessel.
In summary, prior art atherectomy devices adapted to remove atheromatous material or blood clots from an artery all utilize a cutting member having a fixed diameter, the size of which is limited by the size of the opening in the blood vessel through which the device is introduced.
Accordingly, it is an object of the present invention to provide an expandable atherectomy catheter device having a cutting head of variable diameter to accommodate blood vessels having a wide range of internal diameters.
It is another object of the present invention to provide such an atherectomy device for cutting and aspirating atheromatous material, and which may be inserted into a blood vessel in a collapsed state to provide a narrow profile, whereby the device may be introduced into an artery using a standard angiographic percutaneous approach.
It is yet another object of the present invention to provide such an atherectomy device wherein the need for direct surgery to the blocked or narrowed vessel, or the creation of a large opening at the site of insertion into the blood vessel, can both be avoided.
It is still another object of the present invention to provide such an atherectomy device which maybe passed over a guidewire to facilitate insertion of the device into the blood vessel, and advancement of the device to the site of the blockage.
Still another object of the present invention is to provide such an atherectomy device including a coaxial catheter through which the atheromatous material, once cut from the wall of the blood vessel, may be aspirated.
Yet another object of the present invention is to provide such an atherectomy device which permits saline solution or another irrigant to be infused to the site of the cutting head while simultaneously permitting the irrigant and any dislodged atheromatous material to be aspirated.
A further object of the present invention is to provide such an atherectomy device which prevents distal embolization of atherectomized material once cut from the wall of the blood vessel.
A still further object of the present invention is to provide such an atherectomy device which may be used for removal of blood clots, with or without the addition of thrombolytic agents.
Yet another object of the present invention is to provide such an atherectomy device wherein the diameter of the cutting head may be adjusted while the cutting head is being rotated by a motor.